1. Field of the Invention
The present invention relates to a film scanner for reading an image from film and outputting corresponding image data.
2. Description of the Related Art
In the past, various types of film scanners capable of reading an image from film and outputting a video signal (composite video signal, Y-C signal, or the like) of read data have been known. For example, Japanese Patent Laid-Open No. 4-68877 has disclosed an example of a film scanner. A film scanner represented by the disclosed technological means will be described below with reference to FIG. 23. As illustrated, the film scanner includes a CCD control circuit composed of an image sensor 101 such as a CCD for reading an image from film, an A/D converter 102 for converting an image signal read by the image sensor 101 into digital data, and a digital signal processing unit 103a for performing various kinds of signal processing on the digital data and outputting the processed data to a personal computer or the like.
The film scanner further includes a TV display control circuit composed of a frame memory 103b for storing a digital signal processed by the digital signal processing unit 103, a memory control unit 106 for controlling the frame memory 103b, a high-definition TV synchronizing (hereinafter sync) signal generating unit 107, and a D/A converting circuit 104 for reading data stored in the frame memory 103b, converting the data into an analog signal, and outputting a video signal, which can be input to a TV, with a sync signal appended.
As mentioned above, the film scanner has two control units; the CCD control circuit and TV display control circuit.
However, since the two control units (CCD control circuit and TV display control circuit) of the foregoing film scanner are control units in which very fast processing is essential, timing control requires a highly advanced technology.
For example, unless the timing of discharging image data from the frame memory for TV display is precisely synchronous with a horizontal TV sync signal (or blanking signal), jitters occur in a TV display screen. Thus, the TV display screen suffers low definition.
Moreover, unless exposure time control for a CCD is managed reliably, a produced image suffers irregular luminance. This also results in a TV display screen of low definition.
Furthermore, since the two kinds of control are very fast, a single controller cannot perform the respective processing. As mentioned above, therefore, independent control circuits are usually included. That is to say, independent control hardware devices are included. This poses a problem of high hardware cost. Moreover, since the relative timing of the independent hardware devices must be adjusted, there is a possibility that their control sequences may get complicated.